Original Posted By: "Will42"
i have to try and figure out how to get my pictures smaller.Read this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Fuselage length
Pietenpol-List: Fuselage length
Pietenpol-List: Re: Fuselage length
Original Posted By: "K5YAC"
Can someone explain to me how making the fuselage longer compensates for a lighterengine. A lighter engine moves the CG rearward; lengthening the fuselage alsomoves the CG rearward. How does this correlate? I can understand moving thewing back as this would move the CG forward ( I think?) but a longer fuselageseems a move in the wrong direction. WillRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Fuselage length
Can someone explain to me how making the fuselage longer compensates for a lighterengine. A lighter engine moves the CG rearward; lengthening the fuselage alsomoves the CG rearward. How does this correlate? I can understand moving thewing back as this would move the CG forward ( I think?) but a longer fuselageseems a move in the wrong direction. WillRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Fuselage length
Original Posted By: Ameet Savant
Hmmm... moving the wing back would most certainly move the CG back as well. Perhapsyou mean lengthening the engine mount will compensate for a light engine,or lengthening the front of the fuse (?), but if you are light up front, a longertail probably isn't going to help.--------Mark - working on wingsRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Wed, 1 Jul 2009 12:54:07 -0700 (PDT)
Hmmm... moving the wing back would most certainly move the CG back as well. Perhapsyou mean lengthening the engine mount will compensate for a light engine,or lengthening the front of the fuse (?), but if you are light up front, a longertail probably isn't going to help.--------Mark - working on wingsRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Wed, 1 Jul 2009 12:54:07 -0700 (PDT)
Re: Pietenpol-List: Fuselage length
Original Posted By: Rick Holland
"moving the wing back would most certainly move the CG back as well"Sorry, I wrote exactly opposite from what I was thinking on moving the wing. My point is/was, the longer fuselage is recommended for the lighter engines ( Continental;Corvair) and I can't see how this is correct.WillRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Wed, 1 Jul 2009 14:01:13 -0600Subject: Re: Pietenpol-List: Fuselage length
"moving the wing back would most certainly move the CG back as well"Sorry, I wrote exactly opposite from what I was thinking on moving the wing. My point is/was, the longer fuselage is recommended for the lighter engines ( Continental;Corvair) and I can't see how this is correct.WillRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Wed, 1 Jul 2009 14:01:13 -0600Subject: Re: Pietenpol-List: Fuselage length
Re: Pietenpol-List: Re: Fuselage length
Original Posted By: Will42
again, to quote Waldo, "I don't want to be a stickler for accuracy" but moving the wing around is moving the center of lift around, not the CG.Gene ----- Original Message -----
again, to quote Waldo, "I don't want to be a stickler for accuracy" but moving the wing around is moving the center of lift around, not the CG.Gene ----- Original Message -----
RE: Pietenpol-List: Re: Fuselage length
Original Posted By: owner-pietenpol-list-server(at)matronics.com
The center of gravity of the entire airplane needs to be somewhere betweenabout 15% and 33% of the way between the leading edge and trailing edge ofthe wing, in order for the plane to have sufficient stability. If the CG isforward of that range, the tail has insufficent force to be able to raisethe nose to a positive angle of attack and no lift can be generated. If theCG is aft of that range, the plane will have "divergent stability" and willbe uncontrollable.If the CG is too far aft, you can move it forward by moving something heavy(say, the engine, for example) further forward.Did you ever sit on a seesaw as a kid? If there was a fat kid sitting onthe other end, you were left in the air, with your feet dangling helplessly.If you could only move a bit further away from the fulcrum, you couldbalance his mass.Take my word for it - one way to balance a tail-heavy Pietenpol with a lightengine is to make the engine mount longer (within limits - too long and youstart having directional stability issues, requiring a larger verticaltail). Far easier is to shift the wing aft. Even though moving the wingaft tends to move the CG aft as well (just slightly, due to the mass of thewing which has moved aft) it moves the acceptable CG range aft and allowsthe CG to fall within the acceptable range. Very few airplane designs canbe modified in this way - it is one of the great advantages of the Pietenpoldesign. The GN-1 cannot be shifted like the Pietenpol can - there your onlychoice is to move the engine, add ballast or lose weight yourself.Jack PhillipsNX899JP-----Original Message-----
The center of gravity of the entire airplane needs to be somewhere betweenabout 15% and 33% of the way between the leading edge and trailing edge ofthe wing, in order for the plane to have sufficient stability. If the CG isforward of that range, the tail has insufficent force to be able to raisethe nose to a positive angle of attack and no lift can be generated. If theCG is aft of that range, the plane will have "divergent stability" and willbe uncontrollable.If the CG is too far aft, you can move it forward by moving something heavy(say, the engine, for example) further forward.Did you ever sit on a seesaw as a kid? If there was a fat kid sitting onthe other end, you were left in the air, with your feet dangling helplessly.If you could only move a bit further away from the fulcrum, you couldbalance his mass.Take my word for it - one way to balance a tail-heavy Pietenpol with a lightengine is to make the engine mount longer (within limits - too long and youstart having directional stability issues, requiring a larger verticaltail). Far easier is to shift the wing aft. Even though moving the wingaft tends to move the CG aft as well (just slightly, due to the mass of thewing which has moved aft) it moves the acceptable CG range aft and allowsthe CG to fall within the acceptable range. Very few airplane designs canbe modified in this way - it is one of the great advantages of the Pietenpoldesign. The GN-1 cannot be shifted like the Pietenpol can - there your onlychoice is to move the engine, add ballast or lose weight yourself.Jack PhillipsNX899JP-----Original Message-----
Re: Pietenpol-List: Re: Fuselage length
Original Posted By: Ryan Mueller
[quote="generambo(at)msn.com"] again, to quote Waldo, "I don't want to be a sticklerfor accuracy" but moving the wing around is moving the center of liftaround, not the CG. Gene> ---Moving the wing does move the center of lift; it also moves the CG as a resultof the new "moment" of the wing itself. If in doubt, look at a weight and balancework sheet to confirm. And certainly, moving a lighter engine forward moves the CG forward as can be notedby the extremely long noses on turbine conversions, however none of thisaddresses the reason for longer fuselages for the "lighter" engined Piets. It seems the extended engine mount would be a simpler answer than a different fuselagelength; certainly moving the wing aft seems a reasonable solution toan over-weight pilot. WillRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Wed, 1 Jul 2009 19:31:15 -0500Subject: Re: Pietenpol-List: Re: Fuselage length
[quote="generambo(at)msn.com"] again, to quote Waldo, "I don't want to be a sticklerfor accuracy" but moving the wing around is moving the center of liftaround, not the CG. Gene> ---Moving the wing does move the center of lift; it also moves the CG as a resultof the new "moment" of the wing itself. If in doubt, look at a weight and balancework sheet to confirm. And certainly, moving a lighter engine forward moves the CG forward as can be notedby the extremely long noses on turbine conversions, however none of thisaddresses the reason for longer fuselages for the "lighter" engined Piets. It seems the extended engine mount would be a simpler answer than a different fuselagelength; certainly moving the wing aft seems a reasonable solution toan over-weight pilot. WillRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Wed, 1 Jul 2009 19:31:15 -0500Subject: Re: Pietenpol-List: Re: Fuselage length
Re: Pietenpol-List: Re: Fuselage length
Original Posted By: Will42
"Anyone can provide accuracy"------Original Message------
"Anyone can provide accuracy"------Original Message------
Pietenpol-List: Re: Fuselage length
Original Posted By: "Dick N."
I built the long Piet with a Funk powered engine ( Ford B block ) the engine weightwas 257 Lbs. The radiator under the cowl. It flys all day at 87 MPH with2 aboard.The Piet I have now is the short version with a Funk engine, ( upside down ) andthe radiator in the standard position. It would fly 10 MPH slower with 2 aboard,After increasing the HP to over 80 I can now fly at 87 MPH, Take your pick,longer , gives pilot more leg room. Both flys great.Pieti LowellRead this topic online here:http://forums.matronics.com/viewtopic.p ... __________
I built the long Piet with a Funk powered engine ( Ford B block ) the engine weightwas 257 Lbs. The radiator under the cowl. It flys all day at 87 MPH with2 aboard.The Piet I have now is the short version with a Funk engine, ( upside down ) andthe radiator in the standard position. It would fly 10 MPH slower with 2 aboard,After increasing the HP to over 80 I can now fly at 87 MPH, Take your pick,longer , gives pilot more leg room. Both flys great.Pieti LowellRead this topic online here:http://forums.matronics.com/viewtopic.p ... __________
Re: Pietenpol-List: Re: Fuselage length
Original Posted By:> owner-pietenpol-list-server(at)matronics.com
Doesn't moving the wing back move the CG forward relative to the leading edge?Moving the wing back creates a longer nose moment.On Jul 1, 2009, at 5:09 PM, Jack Phillips wrote:> >>> The center of gravity of the entire airplane needs to be somewhere > between> about 15% and 33% of the way between the leading edge and trailing > edge of> the wing, in order for the plane to have sufficient stability. If > the CG is> forward of that range, the tail has insufficent force to be able to > raise> the nose to a positive angle of attack and no lift can be > generated. If the> CG is aft of that range, the plane will have "divergent stability" > and will> be uncontrollable.>> If the CG is too far aft, you can move it forward by moving > something heavy> (say, the engine, for example) further forward.>> Did you ever sit on a seesaw as a kid? If there was a fat kid > sitting on> the other end, you were left in the air, with your feet dangling > helplessly.> If you could only move a bit further away from the fulcrum, you could> balance his mass.>> Take my word for it - one way to balance a tail-heavy Pietenpol with > a light> engine is to make the engine mount longer (within limits - too long > and you> start having directional stability issues, requiring a larger vertical> tail). Far easier is to shift the wing aft. Even though moving the > wing> aft tends to move the CG aft as well (just slightly, due to the mass > of the> wing which has moved aft) it moves the acceptable CG range aft and > allows> the CG to fall within the acceptable range. Very few airplane > designs can> be modified in this way - it is one of the great advantages of the > Pietenpol> design. The GN-1 cannot be shifted like the Pietenpol can - there > your only> choice is to move the engine, add ballast or lose weight yourself.>> Jack Phillips> NX899JP>> -----Original Message-----
Doesn't moving the wing back move the CG forward relative to the leading edge?Moving the wing back creates a longer nose moment.On Jul 1, 2009, at 5:09 PM, Jack Phillips wrote:> >>> The center of gravity of the entire airplane needs to be somewhere > between> about 15% and 33% of the way between the leading edge and trailing > edge of> the wing, in order for the plane to have sufficient stability. If > the CG is> forward of that range, the tail has insufficent force to be able to > raise> the nose to a positive angle of attack and no lift can be > generated. If the> CG is aft of that range, the plane will have "divergent stability" > and will> be uncontrollable.>> If the CG is too far aft, you can move it forward by moving > something heavy> (say, the engine, for example) further forward.>> Did you ever sit on a seesaw as a kid? If there was a fat kid > sitting on> the other end, you were left in the air, with your feet dangling > helplessly.> If you could only move a bit further away from the fulcrum, you could> balance his mass.>> Take my word for it - one way to balance a tail-heavy Pietenpol with > a light> engine is to make the engine mount longer (within limits - too long > and you> start having directional stability issues, requiring a larger vertical> tail). Far easier is to shift the wing aft. Even though moving the > wing> aft tends to move the CG aft as well (just slightly, due to the mass > of the> wing which has moved aft) it moves the acceptable CG range aft and > allows> the CG to fall within the acceptable range. Very few airplane > designs can> be modified in this way - it is one of the great advantages of the > Pietenpol> design. The GN-1 cannot be shifted like the Pietenpol can - there > your only> choice is to move the engine, add ballast or lose weight yourself.>> Jack Phillips> NX899JP>> -----Original Message-----
Re: Pietenpol-List: Re: Fuselage length
Original Posted By: TOM MICHELLE BRANT
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RE: Pietenpol-List: OSH
Original Posted By: Dick N.
DickI reserved space at OSH.Dale----- Original Message -----
DickI reserved space at OSH.Dale----- Original Message -----
RE: Pietenpol-List: Re: Fuselage length
Original Posted By: owner-pietenpol-list-server(at)matronics.com
Dan,Have you run a weight and balance to see where your CG (with you in theairplane) is with respect to the cord of the wing?Moving the wing is very simple, if you made the diagonal cabane struts withsome adjustment for length. The rest of the bracing wires have enoughadjustment in the turnbuckles. Like many others on the list, my wing is aftof vertical by 4". Anticipating that I would have an aft CG problem, Ibuilt my cabane diagonals with adjustment built in.Jack Phillips-----Original Message-----
Dan,Have you run a weight and balance to see where your CG (with you in theairplane) is with respect to the cord of the wing?Moving the wing is very simple, if you made the diagonal cabane struts withsome adjustment for length. The rest of the bracing wires have enoughadjustment in the turnbuckles. Like many others on the list, my wing is aftof vertical by 4". Anticipating that I would have an aft CG problem, Ibuilt my cabane diagonals with adjustment built in.Jack Phillips-----Original Message-----
RE: Pietenpol-List: Re: Fuselage length
Original Posted By: "Bill Church"
Pietenpol-List: Re: Fuselage length
Original Posted By: "Will42"
Well my Corvair really does run after all. I never tried to start it after bringingit home from Arizona over 2 years ago.and I guess it had been at least ayear or two before when DJ ran it last.the tank and lines were really stunk upwith soured up gas.I got everything ready today and put some avgas in-openedthe cut-off valve and heard something hitting the floor-looked over and gas waspouring out of the carb. I took it off and removed the top and cleaned it outand put it back. finally after several attempts it fired up. the throttle stopsweren't set right and I probably had 1/4 throttle or close.good for gettingthe oil pressure and blood pressure up. the tied tail held and I shut it down.after 3 tries I got the throttle stop set right and it purrs like a kitten.I always heard the corvair is smooth but never was close to one running on aplane before.I like it!! now I can't wait to get all the other things sorted outstarting with the cowl. I am not looking forward to that but it has to be done.Ieven got the digital panel to work after some messing with the right wires.I don't like it-doesn't really belong on a Piet but till I fly it some I amnot interested it spending time and money changing anything.but if someone wantsto come to the Texas panhandle and bring good steam gages and swap them outthey are welcome to the digital one.the oil pressure seemed lower than I expected.I was seeing about 37 lb. at about 1100 RPM or less.who knows how accuratethe digital unit is if it isn't calibrated to the sender.I have a mechanicalpressure gage somewhere I can rig to check that.RaymondRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Fuselage length
Well my Corvair really does run after all. I never tried to start it after bringingit home from Arizona over 2 years ago.and I guess it had been at least ayear or two before when DJ ran it last.the tank and lines were really stunk upwith soured up gas.I got everything ready today and put some avgas in-openedthe cut-off valve and heard something hitting the floor-looked over and gas waspouring out of the carb. I took it off and removed the top and cleaned it outand put it back. finally after several attempts it fired up. the throttle stopsweren't set right and I probably had 1/4 throttle or close.good for gettingthe oil pressure and blood pressure up. the tied tail held and I shut it down.after 3 tries I got the throttle stop set right and it purrs like a kitten.I always heard the corvair is smooth but never was close to one running on aplane before.I like it!! now I can't wait to get all the other things sorted outstarting with the cowl. I am not looking forward to that but it has to be done.Ieven got the digital panel to work after some messing with the right wires.I don't like it-doesn't really belong on a Piet but till I fly it some I amnot interested it spending time and money changing anything.but if someone wantsto come to the Texas panhandle and bring good steam gages and swap them outthey are welcome to the digital one.the oil pressure seemed lower than I expected.I was seeing about 37 lb. at about 1100 RPM or less.who knows how accuratethe digital unit is if it isn't calibrated to the sender.I have a mechanicalpressure gage somewhere I can rig to check that.RaymondRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Fuselage length
Re: Pietenpol-List: Re: Fuselage length
Original Posted By: Will42
Guys, forget about the datum. You can make the datum anything you want it to be, and it does not matter. If you want to use all positive numbers, not negative, make it the tip of your spinner.Don't even specify a datum and weigh the airplane. You can calculate the CG as being XX inches aft of the center of the main wheels. (if it is forward, you have a REAL problem) What you then need to calculate is where the CG lands on the wing (so you compare the location of the wing to the CG you just located). This is why most use the leading edge of the wing as a datum, to make this calculation easier.Then, express the location of the CG as a % of the chord. Say you find it is 33% of chord. This is meaningless unless you have published numbers for the CG limits for your specific airfoil which, for the Pietenpol is, surprise, unknown. CAM 18 (who remembers this??) gives the old-time rule of thumb for guessing at a reasonable CG range. Jack stated it correctly, and I don't have it in front of me, but if it is roughly around 33%, give or take a few inches, you are probably all right.This has become way harder than it should be.BTW, everything Jack said is correct.Gene(ducking for cover) ----- Original Message -----
Guys, forget about the datum. You can make the datum anything you want it to be, and it does not matter. If you want to use all positive numbers, not negative, make it the tip of your spinner.Don't even specify a datum and weigh the airplane. You can calculate the CG as being XX inches aft of the center of the main wheels. (if it is forward, you have a REAL problem) What you then need to calculate is where the CG lands on the wing (so you compare the location of the wing to the CG you just located). This is why most use the leading edge of the wing as a datum, to make this calculation easier.Then, express the location of the CG as a % of the chord. Say you find it is 33% of chord. This is meaningless unless you have published numbers for the CG limits for your specific airfoil which, for the Pietenpol is, surprise, unknown. CAM 18 (who remembers this??) gives the old-time rule of thumb for guessing at a reasonable CG range. Jack stated it correctly, and I don't have it in front of me, but if it is roughly around 33%, give or take a few inches, you are probably all right.This has become way harder than it should be.BTW, everything Jack said is correct.Gene(ducking for cover) ----- Original Message -----
Re: Pietenpol-List: Re: Fuselage length
Original Posted By: Ryan Mueller
I did a very thorough weight and balance on my airplane. I suggest that anyonewho does their weight and balance fully understand it before they tackle it.I've seen guys on the list try to get a weight and balance spread sheet fromothers who have done theirs so they can plug numbers in. Not a good idea on mypart. Actually leveling the airplane and weighing at measured points (usuallylanding gear) then finding locations for each arm. Then creating your ownwork sheet is important. Many use arms like the center of the seats for passengerand pilot. Not an accurate or good idea. Much more accurate to actuallyweigh the airplane with yourself or a person while positioned on the seat anddo the math to figure where the arm isThe wing or wing chord itself does not determine the C.G. However if the C.G.is behind the C.L. you are going to have serious problem. Therefore since theC.L. is determined as a % of the chord we typically use the chord as a referenceto determine the % for the C.G. Since Pietenpol wings are seldom positionedin the same place on each and every one we can't just figure where the C.G.is according to the fuselage and gear or weighing points. So in the Pietenpol'scase it is very important to know where the wing is. Knowing what % of thechord that the C.G. of the airplane is, is extremely important.I usually don't pipe up about too many things but a good understanding of weightand balance is very important. I apologize for not being able to explain allthat well but as long as you yourself have a good understanding of it is allthat matters.Don EmchNX899DERead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Thu, 2 Jul 2009 22:04:14 -0500Subject: Re: Pietenpol-List: Re: Fuselage length
I did a very thorough weight and balance on my airplane. I suggest that anyonewho does their weight and balance fully understand it before they tackle it.I've seen guys on the list try to get a weight and balance spread sheet fromothers who have done theirs so they can plug numbers in. Not a good idea on mypart. Actually leveling the airplane and weighing at measured points (usuallylanding gear) then finding locations for each arm. Then creating your ownwork sheet is important. Many use arms like the center of the seats for passengerand pilot. Not an accurate or good idea. Much more accurate to actuallyweigh the airplane with yourself or a person while positioned on the seat anddo the math to figure where the arm isThe wing or wing chord itself does not determine the C.G. However if the C.G.is behind the C.L. you are going to have serious problem. Therefore since theC.L. is determined as a % of the chord we typically use the chord as a referenceto determine the % for the C.G. Since Pietenpol wings are seldom positionedin the same place on each and every one we can't just figure where the C.G.is according to the fuselage and gear or weighing points. So in the Pietenpol'scase it is very important to know where the wing is. Knowing what % of thechord that the C.G. of the airplane is, is extremely important.I usually don't pipe up about too many things but a good understanding of weightand balance is very important. I apologize for not being able to explain allthat well but as long as you yourself have a good understanding of it is allthat matters.Don EmchNX899DERead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Thu, 2 Jul 2009 22:04:14 -0500Subject: Re: Pietenpol-List: Re: Fuselage length
Pietenpol-List: Re: Fuselage length
Original Posted By: "K5YAC"
Thank you Gene! You expressed it better than I could. Knowing where the C.G.falls on the wing (or what % of chord) is what it's all about. Who cares whereit is according to anything else on the airplane.Moving the wing back does not move the C.G. back, only moves it forward, at leastfor aerodynamic purposes. I suppose as it sits on the ground the C.G. willget more aft, but for flight purposes we aren't worried about that. What wereally are doing is moving the fuselage forward in relation to the wing. It'sall about the wing. It's all about the wing.Okay, getting off my soap box now and ducking for cover with Gene!Don EmchNX899DERead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Fuselage length
Thank you Gene! You expressed it better than I could. Knowing where the C.G.falls on the wing (or what % of chord) is what it's all about. Who cares whereit is according to anything else on the airplane.Moving the wing back does not move the C.G. back, only moves it forward, at leastfor aerodynamic purposes. I suppose as it sits on the ground the C.G. willget more aft, but for flight purposes we aren't worried about that. What wereally are doing is moving the fuselage forward in relation to the wing. It'sall about the wing. It's all about the wing.Okay, getting off my soap box now and ducking for cover with Gene!Don EmchNX899DERead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Fuselage length
Original Posted By: Mike Tunnicliffe
Yep this is making more sense... CG in relation to the wing. I was originallythinking of overall CG and the effect on it when moving components.--------Mark - working on wingsRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Fri, 03 Jul 2009 10:07:22 +1200
Yep this is making more sense... CG in relation to the wing. I was originallythinking of overall CG and the effect on it when moving components.--------Mark - working on wingsRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Fri, 03 Jul 2009 10:07:22 +1200
Re: Pietenpol-List: Re: Fuselage length
Original Posted By: Ryan Mueller
fair enough. I do not have their building manual, only an old set of plans. Even this number, though, does not give the CG range, and it is not clear whether their number is arrived at from actual engineering calculations based on the airfoil or just from experience. I would guess the latter. I think Jack McCarthy posted a long, detailed cg calculation on here long ago and gave a cg range from CAM 18. It should be easy to find. Also, I will try to get out my CAM and look it up.Gene ----- Original Message -----
fair enough. I do not have their building manual, only an old set of plans. Even this number, though, does not give the CG range, and it is not clear whether their number is arrived at from actual engineering calculations based on the airfoil or just from experience. I would guess the latter. I think Jack McCarthy posted a long, detailed cg calculation on here long ago and gave a cg range from CAM 18. It should be easy to find. Also, I will try to get out my CAM and look it up.Gene ----- Original Message -----
> Re: Pietenpol-List: Re: Fuselage length
Original Posted By: Dan Yocum